Impulse wrench with angle sensing means

Abstract

In an impulse wrench there is provided an impulse unit with a motor driven inertia drive member, and a movement detecting device arranged to detect an angular movement of the inertia drive member. The movement detecting device includes a rotating disc rigidly connected to and co-rotating with the inertia drive member. The impulse wrench also includes a sensing device including four Hall-element type sensors, and the disc has a rim portion which is magnetised to provide a number of magnetic poles for activating the sensors at rotation of the inertia drive member. The sensors are arranged in pairs such that the delivered signals from the sensors in each pair has a relative phase lag of 180 degrees, and the sensors of one of the pairs are arranged to deliver signals with a phase lag of 90 degrees relative to the sensor signals from the other pair.

The invention claimed is: 
     
       1. An impulse nut runner, comprising:
 an output shaft, 
 a motor with a rotor, 
 an impulse unit connecting the motor to the output shaft and including an inertia drive member rigidly connected to the rotor of the motor, 
 a rotation detecting device comprising a ring element rigidly secured to the drive member and magnetised with a number of magnetic poles equidistantly distributed along a periphery of the ring element, and 
 a sensing device mounted approximately to the ring element and arranged to deliver electric signals in response to passing of said magnetic poles at rotation of the drive member, 
 wherein said sensing device comprises four Hall-elements each delivering a sinusoidal electric signal at rotation of the drive member, and 
 wherein said Hall-elements are disposed in two pairs, and the Hall-elements in each pair are arranged to deliver signals with a 180 degrees phase lag relative to each other and with a 90 degrees phase lag relative to the Hall-elements of the other pair. 
 
     
     
       2. The impulse nut runner according to  claim 1 , wherein said Hall-elements are carried on a printed connector board. 
     
     
       3. The impulse nut runner according to  claim 2 , wherein a circuit board mounted in a housing is connected to said connector board and carries a number of electronic components for treating and forwarding said signals delivered by said sensing device to an operation control unit.